Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

0550192 - ÚFA 2022 RIV CH eng J - Journal Article
Millan, R.M. - Ripoll, J.-F. - Santolík, Ondřej - Kurth, W. S.
Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation.
Frontiers in Astronomy and Space Sciences. Roč. 8, Dec 2 (2021), č. článku 776992. E-ISSN 2296-987X
EU Projects: European Commission(XE) 870437 - SafeSpace
Institutional support: RVO:68378289
Keywords : electron precipitation * plasmaspheric plume * quasi-linear diffusion * radiation belt * wave-particle interaction * whistler-mode hiss/chorus
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 4.055, year: 2021
Method of publishing: Open access
https://www.frontiersin.org/articles/10.3389/fspas.2021.776992/full

In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic ( < 200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the similar to 5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to similar to 2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first similar to 100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L similar to 6), outside of the main plasmasphere.
Permanent Link: http://hdl.handle.net/11104/0325996